New record of Akashiwo sanguinea (Dinophyta) in the tropical estuarine waters of Northeastern Brazil (Western Atlantic).

This study reports the occurrence and the effect of the environmental factors on the spatial and temporal distribution of the dinoflagellate Akashiwo sanguinea (Hirasaka) Hansen & Moestrup in estuarine waters of northeastern Brazil. Samples were collected at seven stations from March 2007 to February 2008 during high tide and low tide, using Van Dorn bottles. The samples were immediately fixed with Lugol and analyzed with the Utermöhl method. Water samples were also collected for the identification of the hydrological characteristics of the area. Akashiwo sanguinea occurred throughout the annual cycle and at all sampling sites with densities ranging between 5 and 410 x 103 cells.L-1. The highest densities were recorded at low tide, especially during the months of the rainy season (July: 210 x 103 cells.L-1; August: 410 x 103 cells.L-1). Density values were within the normal range and blooms were not detected. Despite being common in the area, the species showed preference for sites with high concentrations of orthophosphate and total dissolved phosphorus and with salinity in the mesohaline regime.

Microphytoplankton structure from the neritic and oceanic regions of Pernambuco State - Brazil.

This research was carried out to assess phytoplankton diversity, distribution and ecology on the Pernambuco Continental Shelf and Oceanic region (lat. 7 masculine 33' 00' S to 8 masculine 41' 50' S and long. 34 masculine 04' 47' W to 35 masculine 01' 20' W). Samples were collected during the Joint Oceanographics Projects (JOPS II-Leg 5) by double oblique hauls with a baby bongo net 64 microm mesh size at depth between 14 and 150 m in inshore and offshore waters respectively, in seven transects, totaling 34 stations. The temperature and salinity characterised the tropical water masses. The dissolved oxygen was oversaturated in all stations. The nutrient-low concentrations showed an oligothrophic pattern in the whole area. 173 specific and infraspecific taxa were identified: Dinophyta (103 taxa), Bacillariophyta (61 taxa), Cyanobacteria (7 taxa), Chlorophyta and Chrysophyta (1 taxon). The family Ceratiaceae presented the highest species number (47 taxa). The cyanobacteria Trichodesmium erythraeum Ehrenberg, Oscillatoria spp. and the diatom Leptocylindrus danicus Cleve had higher frequence of occurrence and abundance. Species diversity varied from 0.71 to 3.46 bits.cell-1 and this low index was due to Trichodesmium erythraeum bloom and evenness from 0.14 to 0.65, showing an unstable pattern. The oceanic planktonic species were responsible for the higher richness with 78 taxa, corresponding to 58.39% of the total microphytoplankton. The species association presented two groups. The first one divided in two subgroups: one associated to the neritic/oceanic and oceanic planktonic species and the other to the oligotrophic indicator species. The second group was composed of some key species which were the most abundant and frequent in the area. The first three Principal Component Analyses (PCAs) explained 50.91% of the data variance showing that the area is structured by two groups: one offshore composed by oligotrophic indicators, and another nearshore influenced by continental fluxes.

Determination of eutrophic areas in Mundaú/Manguaba lagoons, Alagoas-Brazil, through studies of the phytoplanktonic community.

Mundaú and Manguaba Lagoons (9 degrees 34' 38'-9 degrees 45' 30' S and 35 degrees 44' 00'-35 degrees 58' 13' W) are considered the largest and most productive ones in the state of Alagoas and were studied with the purpose of identifying the existence of anthropic impacts. Samples were collected at 8 stations, during low tide and flooding in rainy and dry periods, using the 'Van Dorn' bottle and plankton net. In total, 155 taxons were identified, with special emphasis on Bacillariophyta and Cyanophyta divisions. The most abundant species in Mundaú Lagoon was Skeletonema cf. costatum, and in the Manguaba Lagoon, Cyclotella meneghiniana, Microcystis aeruginosa and Anabaena spiroides. The diversity ranged from 0.17 bits cell/L to 4.81 bits cell/L. The predominance of freshwater species (51%), evidenced higher influence of the limnetic flow on the two environments studied. The high values related to the phytoplanktonic density characterize the lagoons as strongly impacted environments, indicating the existence of eutrophic conditions in most of the studied stations.

Phytoplankton nyctemeral variation at a tropical river estuary (Itamaracá-Pernambuco-Brazil).

The Botafogo estuary is of socio-economical importance for Pernambuco State. It is located at the north of Santa Cruz Channel, Itamaracá, Pernambuco, Brazil (07 degrees 42' 50 "S and 34 degrees 52' 10" W). There is a critical need to understand its functioning because of the rate at which this area is being converted to land uses. The phytoplankton dynamics was studied to enhance the knowledge of and verify the possible changes which have occurred in this ecosystem. Sampling was carried out with a plankton net 65 micrometers mesh size for qualitative data, and a Van Dorn bottle for quantitative data. Concurrent hydrological and chlorophyll-a data were collected. Samplings were made in one fixed station in July 1996 (rainy season) and December 1996 (dry season), at 3-hour intervals during 24 hours. Eighty-seven specific and infra-specific taxa were identified from net plankton samples. Diatoms were most frequent, mainly Coscinodiscus centralis and Odontella regia in the rainy and dry seasons, respectively. Phytoplankton density varied from 205,000 to 1,210,000 cell.L-1 in the dry season, and from 230,000 to 2,510,000 cell.L-1 in the rainy season, indicating eutrophic conditions. Most numerically abundant were the diatoms Cyclotella meneghiniana and Cylindrotheca closterium and the phytoflagellates. The ecosystem is polluted, and deleterious effects are minimized by the marine influence which allows periodic water renewal.

Phytoplankton nyctemeral variation at a tropical river estuary (Itamaracá - Pernambuco - Brazil)

O estuário do rio Botafogo tem grande importância socioeconômica para o Estado de Pernambuco. Esse estuário está localizado ao norte do Canal de Santa Cruz, em Itamaracá, Pernambuco, Brasil (07º42'50"S e 34º52'10"W). Há uma necessidade crítica de entender seu funcionamento em razão de a área ser convertida em outros usos. A dinâmica do fitoplâncton foi estudada para aumentar o conhecimento sobre o grupo e verificar as possíveis mudanças ocorridas no ecossistema. Para o estudo qualitativo foram realizadas amostragens com uma rede de plâncton com abertura de malha de 65 micrômetros e, para o quantitativo, utilizou-se uma garrafa de Van Dorn. Paralelamente foram coletados dados de hidrologia e clorofila-a. As amostragens foram feitas em uma estação fixa em julho/1996 (período chuvoso) e dezembro de 1996 (período seco), em intervalos de 3 horas, durante 24 horas. Foram identificados 87 táxons específicos e infra-específicos no plâncton de rede. As diatomáceas foram as mais frequentes, principalmente Coscinodiscus centralis e Odontella regia, respectivamente, nos períodos chuvoso e seco. A densidade fitoplanctônica variou de 205.000 a 1.200.000 céls.Lû1 no período seco, e de 230.000 a 2.510.000 céls.Lû1 no chuvoso, indicando condições eutróficas. A maior abundância numérica foi das diatomáceas Cyclotella meneghiniana e Cylindrotheca closterium e dos fitoflagelados. O ecossistema é poluído e os efeitos negativos são minimizados pela influência marinha, permitindo renovação periódica.